A rotary drive having high torque at a relatively low speed can be obtained from a conventional electric motor, which provides low torque at high speed, by use of appropriate gearing, but this represents an undesirable complication. Alternatively, a high torque, low speed drive can be obtained by a special design of the motor, but this tends to require the motor to be of very large size. It is accordingly an object of the invention to provide an electric motor providing a high torque at low speeds without the use of gearing.
It is also an object of the invention to provide an electric motor of compact construction, in particular in the direction transverse of the drive shaft.
It is also one object of the invention to provide an electric motor which can be energised so as to move an output shaft rotationally about its axis and/or translationally along its axis.